1. Field of the Invention
The invention relates to a method for setting a liquid level in an automatic clothes washer.
2. Description of the Related Art
Automatic clothes washers are ubiquitous. Such appliances clean fabric items effectively, enabling the homeowner to complete other tasks or engage in more satisfying activities while doing the laundry. Modern clothes washers provide a multitude of options for matching a selected cleaning operation to the type of fabric comprising the laundry load and the degree of soiling of the laundry load. This includes setting a liquid level appropriate to the size and fabric type of the laundry load. Modern clothes washers also include sophisticated controllers that are programmed to maximize cleaning efficiency while minimizing water and power consumption. However, despite the capabilities of the modern clothes washer, the appliance remains limited in its ability to set the liquid level based on real-time information relating to the fabric items being laundered.
One type of conventional automatic clothes washer is provided with a drive motor, generally electrically powered, which is used to drive a cylindrical perforate basket during a spin cycle, and a clothes mover during wash and rinse cycles for agitating the laundry load within the basket.
In a conventional automatic clothes washer, cleaning of the fabric items is primarily attributable to three factors: chemical energy, thermal energy, and mechanical energy. These three factors can be varied within the limits of a particular automatic clothes washer to obtain the desired degree of cleaning.
The chemical energy is related to the types of wash aids, e.g. detergent and bleach, applied to the fabric items. All other things being equal, the more wash aid that is used, the greater will be the cleaning effect.
The thermal energy relates to the temperature of the fabric items. The temperature of the wash liquid typically is the source of the thermal energy. However, other heating sources can be used. For example, it is known to use steam to heat the fabric items. All things being equal, the greater the thermal energy, the greater will be the cleaning effect.
The mechanical energy is attributable to the contact between the clothes mover and the fabric items, the contact between the fabric items themselves, and the passing of the washing liquid through the fabric items. In washing machines with a clothes mover, in addition to the clothes mover contacting the fabric items, the clothes mover tends to cause the fabric items to contact themselves, and for the wash liquid to pass through the fabric items. All things being equal, the greater the amount of mechanical energy, the greater will be the cleaning effect.
These three factors can be adjusted to obtain the desired cleaning effect for the anticipated operating conditions and environment. For example, while the direct contact between the clothes mover and the fabric items is beneficial for laundering, it does cause greater physical wearing of the fabric items than the other two factors. Thus, for example, for more delicate clothing, it is desired to reduce the degree of contact. The liquid level in the basket affects all three factors (i.e. chemical energy, thermal energy, and mechanical energy) in the following way: A lower liquid level than required results in more contact between fabric items and the clothes mover and consequently more fabric damage. It also requires less thermal energy to reach to a preselected temperature. Furthermore, for a given amount of detergent, it leads to a more concentrated chemical wash. Conversely, more liquid results in less mechanical energy, more thermal energy, and a less concentrated wash. As a result, in both cases, the performance of the washer will be less than optimal based on the desired combination of the various energies.
Currently, the liquid level is adjusted based on amount of load (either by user or automatically) and even with contemporary washing machines, it has not yet been possible to determine the degree of contact between the fabric mover and the fabric items during the washing process. Thus, contemporary solutions are estimates or empirical data, both of which are typically determined based on a set of standard test conditions. Unfortunately, these standard test conditions are not guaranteed to be repeated when the clothes washer is used by the consumer, resulting in a compromised cleaning result.